Journal of Dental Research http://jdr.sagepub.com/ Variables Affecting the Strength of Bond between Porcelain and Gold Myer H. Lavine and Frederic Custer J DENT RES 1966 45: 32 DOI: 10.1177/00220345660450012501 The online version of this article can be found at: http://jdr.sagepub.com/content/45/1/32 Published by: http://www.sagepublications.com On behalf of: International and American Associations for Dental Research Additional services and information for Journal of Dental Research can be found at: Email Alerts: http://jdr.sagepub.com/cgi/alerts Subscriptions: http://jdr.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav Citations: http://jdr.sagepub.com/content/45/1/32.refs.html Downloaded from jdr.sagepub.com by guest on May 6, 2011 For personal use only. No other uses without permission. Variables Affecting the Strength of Bond between Porcelain and Gold MYER H. LA VINE and FREDERIC CUSTER Department of Dental Materials, Temple University School of Dentistry, Philadelphia, Pennsylvania SYNOPSIS IN INTERLINGUA VARIABLES AFFICIENTE LE LIGAMINAGE DE PORCELLANA FUSIONATE A AURO. Un analyse de certe va- riables demonstrava que si le auro es rendite aspere ante le fusionage de illo con porcellana, un augmento de inter 13 e 15 pro cento pote esser obtenite in le fortia del ligaminage. Quando le agente Ceramcote de conditionage de metallo esseva usate a un temperature de 980 C, le fortia del ligaminage cresceva per 6 a 10 pro cento. Tamen, quando Ceramcote esseva cocite a un temperature de 1050 C, un augmento de 25 pro cento esseva necessari in le carga pro effectuar le fracturation del ligaminage. Le utilisation de un vacuo in le fusionage del porcellana al auro produceva resultatos plus uniforme e un augmento de 11 pro cento in le fortia del ligaminage in comparation con illo obtenite per le normal processo de fusion. In recent years, fused porcelain as a restora- or show bond separation, or the metal may tive dental material has been reexamined by display permanent deformation. many researchers, most of whom think that The investigation of certain manipulative no other dental material can favorably com- procedures was made so that evaluation pete with porcelain as to its esthetic quali- could be made of those variables that could ties and compatibility with oral tissues.1' 2 provide a more optimal bond. These vari- The dental profession is in need of a ables were: (a) preheating the metal to porcelain-fused-to-metal combination that 1,800° F. before the addition of porcelain, as will provide mechanical strength as well as compared to eliminating the preheating; (b) esthetics for veneers used in fixed partial stone-roughened surface compared to cast prostheses. The term "mechanical strength" texture; (c) application of a metal condi- is not used to imply that the porcelain ve- tioner to the castings fired at two different neer contributes anything more than a cos- temperatures, and (d) vacuum and non- metic effect to the restoration. The success vacuum firing of the porcelain. of the restoration is dependent on the design of tooth preparation and the quality of the Materials and Methods metal backing used in respect to its strength Wax patterns of uniform size (26-gauge and the thermal coefficient of expansion.3 thickness, 5 mm. wide and 30 mm. long) Any forces acting on the porcelain-fused- were prepared and sprued. The sprued pat- to-metal combination will result in stresses terns were then invested, using Ceramigold in the restoration. If the external force is Investment* at a constant liquid-powder directed at the metal, the resulting stress radio. within the metal will be transferred through The wax patterns were eliminated by the bond to the porcelain or vice versa.4 heat, using the investment thermal expan- Stress may be caused by (a) cooling or sion technic. The casting rings were heated heating too rapidly; (b) a great difference slowly for 1 hour to a temperature of 7820 C. between the temperature coefficient of the (1,350° F.). The hot rings were allowed to porcelain and metal, and (c) externally ap- heat-soak for 15 minutes at 1,3500 F. plied forces resulting from function. During Ceramco No. 1 goldt was melted with an function, when excessive forces are directed oxygen gas flame and the invested pat- at the porcelain, the porcelain will fracture terns were cast, using a nonvacuum centrif- Presented at the International Association of Dental Re- search Meeting, Pittsburgh, Pa., March 21, 1963. * Whip Mix Corp., Louisville, Ky. Received for publication July 24, 1963. t J. F. Jelenko & Co., New Rochelle, N.Y. 32 Downloaded from jdr.sagepub.com by guest on May 6, 2011 For personal use only. No other uses without permission. Vtol. 45, No, I V.ARIABLES AFFECTING PORCEL.4IN FUSED TO GOLD 33 TABLEt 1 research is now in progress in an attempt IJ)INTIFYING SYMBOLS OF CASTINGS to determine whether oxidation of the metal is actually taking place. The others were not subjected to this process. A metal con- G roup Description ditioner* was used on some of the castings A nouroughened, oxidized. according to the manufacturer's directions. B nonroughened, oxidized; metal conditioner Opaque porcelain, meeasured by the small fired at i 38(s0 F. aperture of a plastic silicate-cement meas- C roughened, oxilizecl. D roughened, nonoxidized; metal conditioner uringy device, was mixed with distilled water fired at 1,800° F. and placed on the 5-mm. by 15-mm. areas. E roughened, oxidized; metal conditioner fired Small rectangular pieces of 28-gauge green at 1,800hF. wax were attached to the castings at the F roughened. oxidized; metal conditioner fired scratch marks to limit the porcelain to the at 1,8000 F., vacuum baked. G roughened, oxidized; metal conditioner fired predetermined marked area during vibrat- at 1,800° F., multiple vacuum baked. ing condensation (Fig. 2). it roughened, nonoxidized; metal conditioner fired at 1,925' F. I roughened, oxidized; metal conditioner fired at 1,925°oh . uagal casting machine. After the casting was completed, the ring was quenched in water as soon as the button emitted a dull red glow. The cast ings were cleaned, using ultra- sonicnmethods and were inspected for de- fects that could influence the end result. For ty-three individual castings weremneas- ured and marked 5 mm. and 20 mm. from the end opposite the sprue end, using a Boley gauge. Identifying symbols were placed on the CaStillgS (Table 1). The FIcG 2. Firing of the opaque porcelain marked-off 5-by-15- mm. areas were rough- ened with a heatless stone or left as they After drying, the wax xvas removed from were cast (Fig. 1). Thirty-three castings the samples, which. were placed on a silica were heated to 1,8000 F. in a porcelain oven slatb in a porcelain furnace (preheated to and kept at that temperature for 20 min- 1,200' F.) and kept there for approximately utes, thereby subjecting them to what we 8 minutes, until they were fired to 1,8000 F. regard as an oxidative-type process. Further After cooling, the body or gingival porcelain measured by the large aperture of the sili- cate-cement measuring device was con- densed on the opaque porcelain and fired in the same way (Fig. 3). The testing apparatus (Fig. 4), a modified form of the transverse tester for denture base resins in the American Dental Associa- tion Specification No. 12, was used so that the porcelain-gold bond would be subjected to vulnerable tensile stress from increased bending forces (Fig. 5). The bending forces would cause the porcelain to separate from the casting or to fracture. If the bond proved sufficient, the porcelain would crack (Fig. 6). The deflections gauge was placed on zero, and FIG. 1.-- Preparation of the castings * Ceramcote, Ceramco, Inct, Woodside, N.Y. Downloaded from jdr.sagepub.com by guest on May 6, 2011 For personal use only. No other uses without permission. 3-1 LZI 171NE AND CUSTER J. dent I. Res. January-Februtary 1066 Fusion of 1)0(1)~~~~~~~~~~~~~~~~~~~~~.. 3 Vie.. . .orclai 100 Gm. of shot in a paper CuP was placed on the testing table. At the end of each Finute a reading of the deflection gauge record, ad another 100 Gn of shot was was ad~ded. 'lhe weight, time and clefiec- tions were recorded when the sample failed. Results When the roughened, oxidized, condi- tioned samples (Group E, Table 2) were compared with the rougyhened, oxidized sam- ples (Group (7, Table 2), and the smooth, FI. 'S. A testedl sample showigspraino oxidized, conditioned samples (Group B, the jsorcelain from the casting. Table 2) were compared with the smooth, oxilizec samples (Group A, TaLblce 2), the metal conditioner (subjected to 1,St00 F'. firing) increased the bond strength 10 per cent,and 6 per cent, respectively. The con- ditioner sub jectec to l,925' F. firing (Grou1p I, Table 2), had 24 per cent greater bond strength than the conditioner subjected to the 1,800' F. firing (G'roup E, Table 2). The n .h .o ......dbond strength of roughened, metal-condi- tioned samples fired at 1,925' F. (Group H, ~~Table 2) had ain increase of 26 per cent when compared with the roughened, metal condi- tioned samples fIred at t,8000 F. (Group D, Table 2). Vacuum baking of the porcelain (Group F, Table 2) gave 11 per cent grea,~ter bond strength than the regular backing pro- cedure (GC'roup E, Table 2). Wtx- aE incl firing) bond strength of the samples having elsefltThe the casting rtiungheied tGi;oup C, Table 2) waIs 13 per cent greater than that of the nonroughened samples (G'roup A, Table 2) xvhen the castings were subjected to heat conditioning. When the metal conditioner ie.. 4.- Testing apparatus was added after heat conditioning, the Downloaded from jdr.sagepub.com by guest on May 6, 2011 For personal use only. No other uses without permission. Vol. 45, No. I VVARIABLES AFFECTING PORCELA IN Ft SED TO GOLD 35 -akU FIG. 6. -Two samrl-les illustrating separation and cracking of the porcelain, respectively rotughened samples (Group E, Tal le 2) had operator can, with experience, reduce the 15 per cent greater bondt strength as com- chances of possible failure if he adheres to pared with the nonrouighened samples the specific instructions of the manufac- ((rotup 13, Table 2). This shows that, in turer2' If the thermally induced stresses are this instance, the LISe of metal cotiditioner eliminated, the success of the restoration is increased the bond strength by 2 fxer cent. more dependent on the design of the tooth preparation and cast metal framework. Discussion Residual stresses are still present but are For porcelain-ftfsed-to-metal restedorat ions believed to be minimal. the maniptlative procedures must b e highly The manner of testing bond strength disciplined to achieve satisfactory results. appears to simulate oral conditions. The The nature of the materials is such that the transverse test is directed to the metal, and the resultant forces are directed to the porce- FT\BLE 2 lain in a tensile stress. Porcelain is known to have lesser tensile strength than com- FEI,"CTS OF VARIABIIESS ON BoBN ) STIRENGITH pressive strength. The actual deflection of the metal has Average been established.5 Because gold has an ex- Load at tremtely high modulus of elasticity, there .No. of Distribution of Separation was a minimal amount of deflection. The (.roup Samples (G m Bond (Gm.)a length between the supports of the testing Gm)_ A\ 5 800; 900; 900; 1,000 900 apparatus, the width, and the thickness of B 4 900; 1,000; 1,000; 1,100 960 the castings were all constant; actually, C 5 1,0(0; 1,000; 1,000; therefore, the adhesion of the bond was 1tIG0, 1,200 1,040 measured. 1) 5 800; 900; 1,000; 1,1(1)0; The thickness of the opaque and gingival 1,200; 1,200) E 5 900; 1,000; 1,100; 1,200; 1,060 porcelain could also affect the results; there- 1,300; 1,400; 1,500 1,140 nite areaexact was equal to used over athick- fore, an that amount was a uniform defi- F 5 1,000; 1,100; 1,200; 1300; 1,400; 1,500; ness measured as 1.2 mm. and checked with 1,500 1,28t) a Boley gauge. The thickness of 1.2 mm. G 5 1,200; 1,200; 1,300; would be that, of a veneer in the oral cavity. H 5 1,300; 1,400 1,200; 1,300; 1,400; 1,280 The data were subjected to a statistical 1,500; 1,600 1,440 analysis of variance that is not includedThe be- I 4 1,100; 1,200; 1,300; cause of the clinical basis of this report. 1,400; 1,500; 1,600; statistical analysis, however, showed a true 1,700; 1,700; 1,800 1t,0o difference between the different technics used. Downloaded from jdr.sagepub.com by guest on May 6, 2011 For personal use only. No other uses without permission. 36 LA VINE AND CUSTER J. dent. Res. January-February 1966 Summary metal conditioner was fired to 1,9250 F., a For good results with porcelain fused to 25 per cent increase in load was necessary gold, the technician must be thoroughly to fracture the bond. familiar with the materials, maintain a strict This work demonstrated that the most discipline in manipulating the materials, and important factor affecting the strength of follow the manufacturer's directions in de- bond between porcelain and gold was high- tail. temperature firing of the metal conditioner. Design of the tooth preparation and the Surface roughness and oxidation were lesser metal restoration or framework are factors factors. Additional vacuum-firing trials are that probably influence the success of needed to prove an influence on bond the porcelain-fused-to-gold restoration more strength due to vacuum firing. than do the actual materials used. By subjecting the gold-porcelain samples References to a transverse test, the porcelain actually 1. DUNSWORTH, F. D. Porcelain Fused to Gold. J. prosth. was placed under a state of tension, allowing Dent., 8:635-39, 1958. 2. BRECKEuR, S. C. Improved Porcelain Fused to Gold measurement of bond strength. Bridges. Dental Clinics of North America, March, Roughening the castings before the addi- 1959, 163-73. tion of opaque and gingival porcelain re- 3. SILVER, M. An Evaluation and Comparison of Porce- lains Fused to Cast Metals. J. prosth. Dent., 10:1055- sulted in 13 to 15 per cent greater bond 64, 1960. strength as compared with nonroughened 4. CUSTER, F. The Effect of The Gold Oxidation Process in The Porcelain Fused-to-Gold Bond. Thesis, Uni- castings. versity of Michigan School of Dentistry, 1961. The bonding agent fired at 1,8000 F. had 5. ASGAR, K., PEYTON, F. E. The Effect of Certain Vari- 6 to 10 per cent greater bond strength than ables in the Bond Strength of Porcelain Fused to Gold, Abstract M34, read at the annual meeting of the the castings without the agent. When the International Association for Dental Research, 1962. Downloaded from jdr.sagepub.com by guest on May 6, 2011 For personal use only. No other uses without permission.